Two kinds of sudden gains in brief psychotherapy

Sudden gains (SGs) are known to predispose to good outcome in psychotherapy, especially in brief treatment. However, some SGs may be illusory, in the sense that they arise from measurement error in the context of gradual change. We examined change before, during, and after SGs that were either true or illusory.

In a sample of 1,867 university students treated with brief psychotherapy, we simulated session data as gradually changing score sequences, identified artifactual SGs therein, and utilized the simulated data to categorize actual participant SGs as either illusory or true.

During treatment, participants with illusory SGs (N = 42) improved as much as did participants with true SGs (N = 67). Moreover, late in treatment participants with SGs and their matched controls improved at similar rates. True SGs were preceded by more distress and were larger than illusory SGs. Among participants with true SGs, very large SGs were more likely to reverse later in treatment.

Relatively small SGs may reflect measurement error. When brief psychotherapy patients deteriorate early in treatment but then suddenly experience substantial improvement, little further change is to be expected.